This invention relates to a safety brake for a pulley and more particularly to a safety brake for a cable pulley of a carpet rack.
Where a rack is employed for displaying carpets using cables to raise and lower the carpets and support structures, there is a risk that the cables may become damaged or worn and break, with the falling carpet and support structure potentially resulting in damage to property or persons near the rack. A standard means of providing a safety brake entails the use of electrical sensing means to detect the cable absence from a given point in its usual course.
The development of the present invention was necessitated by the limitations of the standard cable braking means, as the standard means is unnecessarily complex and forces reliance on electrical detection.
In response to this problem, the present invention provides a relatively simple mechanical means for preventing damage due to cable failure, namely a carpet rack safety brake assembly as described below.
A carpet rack of the type having cable and pulleys for lifting carpets is disclosed in Canadian Patent No. 2,090,354 by the same inventor. In this prior patent, a worm gear winch is relied on to provide self-braking so that the winch drum cannot accidentally run free and allow the carpet support arm to descend rapidly.
It is also considered desirable, however, to prevent rapid descent of the carpet support arm in the event of a broken cable. Known cable brakes such as that shown in U.S. Pat. No. 5,513,723 are not entirely satisfactory due to reliance on electrical detection brake operators in the event of cable failure.
The principal object of this invention is to provide relatively simple mechanical means for preventing personal or property damage due to cable failure in a carpet display rack. Other objects will appear from the description and the drawings.
Accordingly, the present invention provides a safety brake assembly comprising a housing movable on a vertical support, the housing attached to a carpet support arm, a pulley rotatably mounted on a shaft of the housing, a link having an inner end pivotally connected to the shaft and an outer end connected to a first end of a pivot bracket on the housing, a second end of the pivot bracket connected to a wedge-shaped member adjacent the pulley, and tensioning means connected intermediate the ends of the pivot bracket. In the event of cable failure, the upward pressure previously exerted on the pulley is released, causing a downward movement of the pulley and link, so that the movement is transferred by means of the pivot bracket to cause upward movement of the wedge-shaped member which is forced between the pulley and the vertical support, the resultant friction arresting further downward movement of the housing and carpet support arm.